The shipment of goods by various carriers including aircraft, ships, railroad, trucks and the like typically involve the use of standardized shipping containers that can be transferred from one carrier to another. The development of shipping containers that have a standardized shape and size allows for the similar treatment of the shipping container regardless of where in the world or what type of carrier is being used. Thus, goods can be efficiently shipped around the world without having to transfer the contained goods from one shipping container to another. Thus a shipping container may be initially loaded, then placed on and then transferred to a series of carriers until reaching a final destination, all without handling the goods loaded in the shipping container.
The transfer of the shipping container between carriers or staging areas increases the time it takes to ship goods from the point of origin to the final destination point. Transfers are especially burdensome when the transfer is not accomplished by heavy-duty lifting equipment, such as cranes, that can easily hoist and move a shipping container. For example, many transfer and final destination points do not have a crane for the loading or off-loading of a shipping container from a flatbed of a semi-trailer truck and therefore require some type of jack or other similar lifting apparatus. Further, a jack or other similar lifting apparatus may be required to be transported to a stalled or broken-down truck in order to transfer the shipping container to another truck. Currently there is no simple, portable, lightweight, easily installed device capable of lifting a fully loaded shipping container sufficiently to remove it from or replace it upon a flatbed trailer or chassis.
In addition, the conventional lifting apparatus generally includes a three-part telescoping device with two moving parts positioned within a container or barrel. The smaller of the two moving parts is enclosed within the larger of the two moving parts. Hydraulic pressure applied to a container acts against the two moving parts simultaneously. The result is that the larger of the two moving parts moves first because it has a larger area. Once the larger of the two moving parts reaches its maximum extension the smaller of the two moving parts begins to move.
One of the problems with this type of device is an action called staging. Because the hydraulic fluid is generally applied to the lift device at a fixed continuous rate the two moving parts move at different rates depending upon the difference in their areas. As stated above, the larger of the two moving parts moves first, and because it is the larger of the two areas it moves with more force but less speed than the second moving part. When the first moving part reaches its full extension and stops moving the second moving part begins to move at a much lower force but a higher speed than the first moving part. The large difference in area between the first moving part and the second moving part causes the object being moved to move erratically when the device changes stages (i.e., when the first moving part stops and the second moving part begins its movement).
Furthermore, the conventional telescoping device is large and heavy due to the many moving parts adding to the weight of a lifting assembly. The overall dimensions are large such that these devices cannot be used in space-limited applications. Rather, smaller conventional non-telescoping devices would be necessary. As a consequence, the space-limited applications would then be limited as to the full extension length that can be achieved.